The present invention relates to a power switching apparatus for switching power supply sources for a vehicle air conditioner that can receive a power supply from a plurality of power sources.
A vehicle air conditioner mounted on a vehicle has a pre-air conditioning function in which the operation of the air conditioner is started before start of running of the vehicle (for example, see JP-A-2000-078701). In order to operate the pre-air conditioning function, a supply power to the vehicle air conditioner must be stably ensured even during stopping of the vehicle. Therefore, the pre-air conditioning function is often mounted on an electric vehicle or plug-in hybrid vehicle (hereinafter, generally referred to as “electrically driven vehicle”) which, even during stopping, can get an electric power from an external power source.
JP-A-2000-078701 discloses a technique in which pre-air conditioning is efficiently performed to make the cabin comfortable at start of running, and to suppress power consumption of a battery during running. More specifically, an operation signal output from a charger mounted on the vehicle (vehicle charger), and a pre-air conditioning switch are checked to determine whether the vehicle charger is performing the charging operation or not, and further determine the charging power. If the vehicle charger is performing the charging operation and pre-air conditioning is selected, pre-air conditioning is performed. When pre-air conditioning is to be performed, determination is made on the charging power, and the air conditioning ability which is set in accordance with the charging power is selected. This enables pre-air conditioning to be performed in preference to charging of a battery. Even when the charging power is low, therefore, pre-air conditioning is performed without consuming the power in the battery.
In the above-described related art, however, there is a problem in that the user cannot select a power supply source for an electric power to the vehicle air conditioner in the operation of pre-air conditioning. In a vehicle air conditioner of the current status of the art, in a state where a charging cable is connected to a charging port of a vehicle, only an external power source is used as a power supply source for the vehicle air conditioner in the operation of pre-air conditioning, and, in a state where the charging cable is not connected to the charging port, only the electric power in a battery mounted on the vehicle (vehicle battery) is used. In the current status, means for enabling the user to control the power supply source for a vehicle air conditioner is limited to connection of a charging cable. Therefore, the present art cannot comply with various needs for the pre-air conditioning function.
When pre-air conditioning is operated by using only an external power source, for example, the air conditioning ability of a vehicle air conditioner is limited, and therefore air conditioning is insufficiently performed when the temperature is extremely high or low. Consequently, there seems to be a need for, when the temperature is extremely high or low, ensuring a sufficient air conditioning ability by using the power in a vehicle battery. Moreover, there seems to be another need for enabling the vehicle battery to be charged by low-cost nighttime electric power, and using the charging power in pre-air conditioning to reduce the running cost of a vehicle. In the current status, these needs cannot be satisfied on the side of a vehicle air conditioner, and are satisfied by, for example, user's manual operations of connecting and disconnecting a charging cable.